With development of mobile communications technologies, the 3rd Generation Partnership Project (3GPP for short) imposes higher requirements on a peak data rate and a system bandwidth and the like. To satisfy the requirements, carrier aggregation (CA for short) is introduced in a 3GPP Long Term Evolution Advanced (LTE-A for short) system. CA may acquire a higher bandwidth by aggregating multiple contiguous or non-contiguous component carriers (CC for short), thereby increasing the peak data rate and a system throughput. In a carrier aggregation system, when user equipment (UE for short) works on multiple carriers, an eNB is allowed to schedule a part or all of the carriers for the UE to perform uplink transmission simultaneously. In this case, for proper scheduling by the eNB, the UE needs to report its power headroom (PH for short).
CCs in CA may be provided by a same base station (called intra-base station CA), or may also be provided by different base stations (called inter-base station CA). In an existing LTE-A standard, for intra-base station CA, after a power headroom report (PHR for short) is triggered, the UE sends the PHR in any serving cell, where the PHR includes information such as a power headroom reserved for each serving cell. The base station receives the PHR, and may estimate a downlink path loss of the UE in each serving cell and coordinate uplink resource allocation of each serving cell. For inter-base station CA, after a PHR is triggered, the PHR sent by the UE in any serving cell can be received by only one of the base stations, and a base station receiving the PHR does not know an allocation status of uplink resources of other base stations and cannot coordinate an uplink resource of each serving cell. Consequently, a problem of transmission resource waste and low transmission efficiency is caused.